This invention relates in general to the field of machine tools and deals more particularly with a fixture which is used to accurately position a workpiece during machining operations and which is specially constructed to be set up by a robotic machine.
Machine tools such as milling machines, drilling machines and boring machines typically include a work table on which the workpieces are held while they are being machined. In order for the machining operation to be carried out accurately, it is necessary for the workpiece to be positioned precisely on the work table relative to the tool. In the past, various types of jigs and other fixtures have been used to provide stop surfaces against which the workpiece can be held to locate it in the proper position.
One type of fixture that has been used includes stop pins and a table having holes for receiving the pins at various locations, as shown in U.S. Pat. No. 3,049,345 to McFerren. By placing the pins in different holes, stop surfaces can be established for properly locating workpieces having various sizes and shapes. Although this type of fixture is generally satisfactory in many types of machining operations, it is subject to a number of problems. In order to position the work accurately, the pins must fit closely in the receiving holes, and this requires close tolerances in the pins and the holes. In addition, the pins must be precisely aligned with the holes in order to enter them. While human operators do not have great difficulty in inserting the pins, the robotic machines are difficult to program accurately enough to permit the robot to precisely align the pins with the holes. Consequently, robotic machines are not able to set up the fixture for machining operations, and this drawback has inhibited advances in the field of robotically operated machinery.